Technical Field
The present disclosure relates to a wide bandgap semiconductor switching device, which has a wide area Schottky junction; further, the present disclosure relates to the process for manufacturing the aforementioned switching device.
Description of the Related Art
As is known, there are today available so-called “Junction-barrier Schottky” (JBS) power diodes, also known as “Merged PiN Schottky” (MPS) diodes. According to this technology, a diode forms two distinct contacts: an ohmic contact and a Schottky contact.
Generally, JBS diodes are of silicon carbide. In particular, as described, for example, in the U.S. Patent Publication No. 2015/0372093 in the name of the present applicant, a JBS diode includes a semiconductor body of silicon carbide of an N type, which is delimited at the top by a front surface, over which a conductive layer extends, formed, for example, by titanium. Present within the conductive layer, and in contact with the front surface, is a plurality of conductive regions, made, for example, of nickel silicide. Further, formed within the semiconductor body are wells of a P type, which extend from the front surface of the semiconductor body so that each well contacts a corresponding conductive region. In this way, between each conductive region and the corresponding well an ohmic contact is created. In addition, between the conductive layer and the portions of semiconductor body arranged between the wells, corresponding Schottky contacts are formed.
The JBS diodes described above substantially have, at the working current, the same voltage drop as a Schottky diode. Furthermore, in reverse biasing and in the proximity of breakdown, JBS diodes exhibit a leakage current comparable with the leakage current of a bipolar diode. In addition, the presence of the ohmic contact enables JBS diodes to withstand, in forward biasing, high currents, thanks to the fact that the bipolar junction is activated. However, the presence of the ohmic contacts involves the need to align the conductive regions and the corresponding wells precisely. Furthermore, the overall area of ohmic contact is limited by the quality of the alignment. This limit reflects upon the possibility of increasing the density of the wells. In addition, the presence of the wells causes a reduction of the useful area for creation of the Schottky contact, with consequent reduction of the possibility of reducing the voltage drop across the diode, at the working current.